Sebastian Vettel is not expecting to repeat his Singapore Grand Prix performance this weekend in Korea after he was pipped to the fastest Friday practice time by Mercedes' Lewis Hamilton.

Vettel finished the session 0.108s off the pace of Hamilton in second practice and looked evenly matched with the Mercedes over longer runs.

"Overall I'm pretty happy and we had a solid day, but surely there is room for improvement and I think it will be very close this weekend with Mercedes," Vettel said.

The Korean International Circuit offers a very different challenge to Singapore two weeks ago and Vettel is expecting a close fight.

"Singapore was exceptional in many ways and it was closer today. Obviously you don't know what other people are doing with fuel loads, but give or take 10 kilos up or down it is still quite close. Tomorrow in qualifying it will be tight, especially as Mercedes is always performing very well in qualifying."